Who was the leading American composer and conductor of band music?

The leading American composer and conductor of band music was John Philip Sousa. Often referred to as the "March King," he is best known for his military marches, such as "The Stars and Stripes Forever" and "Semper Fidelis." Sousa's contributions significantly shaped the genre of concert band music and popularized the American march style in the late 19th and early 20th centuries. His legacy continues to influence band music and performance today.